1. Prior Art
The prior art is believed to be best exemplified by the following patents:
______________________________________ Tolaas 3,876,131 4/8/75 Hodges 2,777,769 1/15/57 Moffett 2,633,284 3/31/53 Levinson 3,777,099 12/4/73 Gottsos 4,013,798 3/22/77 Ferree 3,398,041 8/20/68 Kuchenbecker 4,096,948 6/27/78 Faust 4,141,487 2/27/79 Virnig 3,672,916 6/27/72 ______________________________________
Patent Application:
Mitchell, Ser. No. 971,318 filed Dec. 20, 1978, now U.S. Pat. No. 4,210,674.
2. Background of the Invention
This invention relates to an improvement in convenience food packages adapted to contain a product which may be subjected within the package to elevated temperatures.
In the preparation of refrigerated packaged food for serving in a heated state, it has been the practice to place the packaged food in a microwave oven to heat the same. Heating may be either for the purpose of thawing and cooking frozen foods or for thawing and heating cooked foods. In either event, considerable water vapor pressure is generated, and since packages are usually well sealed while stored, precautions are usually taken to ensure against sudden explosions by providing for adequate venting of the package. One means that has been utilized comprises building weakened areas in the package seals that rupture on buildup of water vapor pressure. Another means has been in the form of a plastic cover or coating over an aperture that is removed physically prior to using the package or which has been oriented to have a memory and which retracts on exposure to certain temperatures.
U.S. Pat. No. 4,141,487 is believed material to the examination of this application in its disclosure of a package for enclosing a food product wherein a continuous layer of plastic film forms the upper wall surface of the package, has a fold over section to form at least one pleated section having an interior fold line and an elongated opening passing through the layer along the fold line for venting gas during cooking. An adhesive sealant material seals the pleated section until a predetermined temperature is reached, at which time the sealed pleated section opens to expose the opening and vent the package. In this disclosure, the vent aperture is left open and is sealed off by the fold-over section of material. The package requires additional material and distorts because pressure builds up in the pouch to force the foldover to unfold thereby freeing the vent aperture after the sealant holding the foldover in place has melted. Materials employed as sealants melt within the range of 120.degree. F. to 150.degree. F.
Packages embodying the above described means are subject to distortion by pressure generated within the pouch or package before venting occurs.
A package for containing vapor-generating materials that remains substantially flat during use is highly desirable for some applications, for example, wherein such vapor-generating materials are contained in a package within a package and space or other considerations necessitate that the package vent without substantial distortion or pillowing.
It is an object of this invention to provide a material suitable for production of a package that is capable of venting vapor generated therewithin without substantial distortion of the package.
It is a further object of this invention to provide a package or component thereof formed from such material.
Yet another object is to provide a method for producing such material.